This invention relates to electroless plating operations and, in particular, to testing the suitability of material for such operations.
Electroless copper plating is an important step in the fabrication of printed circuit boards. Typically, pan of the fabrication sequence involves depositing a solder mask material over the board which includes copper pads and leads on one or more major surfaces, and leaving the pads exposed for later soldering. The exposed copper is then electrolessly plated to achieve the full thickness of any via holes and adjust plating heights to solder mask planarity.
One of the problems which can occur is "encroachment" where the solder mask lifts up during plating resulting in poorly adhered solder mask. Plating cycles are typically of the order of 12 hours and often provide inconclusive results for determining whether a particular solder mask material is unsuitable. Thus, it is desirable to have a quick method for determining whether a mask material will adhere to the board and metal layers during an electroless plating process.